J/A+A/699/A32 NLTE corrections for metal-poor stars (Koutsouridou+, 2025)
Large databases of metal-poor stars corrected for three-dimensional and/or
non-local thermodynamic equilibrium effects.
Koutsouridou I., Skuladottir A., Salvadori S.
<Astron. Astrophys. 699, A32 (2025)>
=2025A&A...699A..32K 2025A&A...699A..32K (SIMBAD/NED BibCode)
ADC_Keywords: Stars, population II ; Stars, metal-deficient ; Abundances
Keywords: catalogs - stars: abundances - stars: atmospheres -
Galaxy: abundances - Galaxy: evolution
Abstract:
Early chemical enrichment processes can be unveiled by the careful
study of metal-poor stars. In our Local Group, we can obtain spectra
of individual stars to measure their precise, but not always accurate,
chemical abundances. Unfortunately, stellar abundances are typically
estimated under the simplistic assumption of local thermodynamic
equilibrium (LTE). This can systematically alter both the abundance
patterns of individual stars and the global trends of chemical
enrichment. The SAGA database compiles the largest catalogue of
metal-poor stars in the Milky Way. For the first time, we provide the
community with the SAGA catalogue fully corrected for non-LTE (NLTE)
effects, using state-of-the-art publicly available grids. In addition,
we present an easy-to-use online tool NLiTE that quickly provides NLTE
corrections for large stellar samples. For further scientific
exploration, NLiTE facilitates the comparison of different NLTE grids
to investigate their intrinsic uncertainties. Finally, we compare the
NLTE-SAGA catalogue with our cosmological galaxy formation and
chemical evolution model, NEFERTITI. By accounting for NLTE effects,
we can solve the long-standing discrepancy between models and
observations in the abundance ratio of [C/Fe], which is the best
tracer of the first stellar populations. At low [Fe/H]←3.5,
models were unable to reproduce the high measured [C/Fe] in LTE, which
are lowered in NLTE, aligning with the simulations. Other elements are
a mixed bag, where some show improved agreement with the models (e.g.
Na) and other appear even worse (e.g. Co). Few elemental ratios do not
change significantly (e.g. [Mg/Fe], [Ca/Fe]). Properly accounting for
NLTE effects is fundamental for correctly interpreting the chemical
abundances of metal-poor stars. Our new NLiTE tool, thus, enables a
meaningful comparison of stellar samples with chemical and stellar
evolution models as well as with low-metallicity gaseous environments
at higher redshift.
Description:
Using the NLiTE tool (https://nlite.pythonanywhere.com/) we have
computed non-LTE (NLTE) corrections for 22 chemical species, for all
Milky Way metal-poor (MP; [Fe/H]≤-1) stars in the SAGA database
(http://sagadatabase.jp/). NLiTE is based on publicly available NLTE
grids and provides average NLTE corrections for the most commonly used
spectral lines depending on the stellar atmospheric parameters (Teff,
logg, [Fe/H], [X/Fe]).
table1.dat lists the spectral lines most commonly used in observations
of MP stars, for which NLTE corrections are available in the
literature.
table2.dat contains the NLTE-corrected abundances of all individual MP
SAGA stars.
table3.dat contains full details for our NLTE corrections for all MP
entries in SAGA (multiple entries may correspond to the same star).
table4.dat contains the coordinates and stellar atmospheric parameters
of all MP SAGA entries.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 11 282 Spectral lines most commonly used in observations
of MP stars, for which NLTE corrections are
available in the literature
table2.dat 462 2314 NLTE-corrected abundances of all individual
MP SAGA stars
table3.dat 121 405185 Full details for our NLTE corrections for all
MP entries in SAGA (multiple entries may
correspond to the same star)
table4.dat 147 7367 Coordinates and stellar atmospheric parameters
of all MP SAGA entries
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 A4 --- Ion Species identifier
6- 11 F6.1 0.1nm lambda Wavelength λ; in Å
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star identifier
27- 68 A42 --- Ref Reference of the source paper
70 A1 --- l_A(Li) ? Limit flag for A(Li)
72- 76 F5.2 --- A(Li) ? NLTE absolute Li abundance
78- 81 F4.2 --- e_A(Li) ? Uncertainty on A(Li)
83 A1 --- l_[C/Fe] ? Limit flag for [C/Fe]
85- 89 F5.2 --- [C/Fe] ? NLTE [C/Fe] abundance ratio (1)
91- 94 F4.2 --- e_[C/Fe] ? Uncertainty on [C/Fe]
96 A1 --- l_[CH/Fe] ? Limit flag for [CH/Fe]
98-102 F5.2 --- [CH/Fe] ? NLTE [CH/Fe] abundance ratio (1)
104-107 F4.2 --- e_[CH/Fe] ? Uncertainty on [CH/Fe]
109 A1 --- l_[CI/Fe] ? Limit flag for [CI/Fe]
111-115 F5.2 --- [CI/Fe] ? NLTE [CI/Fe] abundance ratio (1)
117-120 F4.2 --- e_[CI/Fe] ? Uncertainty on [CI/Fe]
122 A1 --- l_[N/Fe]LTE ? Limit flag for [N/Fe]
124-128 F5.2 --- [N/Fe]LTE ? LTE [N/Fe] abundance ratio (2)
130-133 F4.2 --- e_[N/Fe]LTE ? Uncertainty on [N/Fe]
135 A1 --- l_[O/Fe] ? Limit flag for [O/Fe]
137-141 F5.2 --- [O/Fe] ? NLTE [O/Fe] abundance ratio
143-146 F4.2 --- e_[O/Fe] ? Uncertainty on [O/Fe]
148 A1 --- l_[Na/Fe] ? Limit flag for [Na/Fe]
150-154 F5.2 --- [Na/Fe] ? NLTE [Na/Fe] abundance ratio
156-159 F4.2 --- e_[Na/Fe] ? Uncertainty on [Na/Fe]
161 A1 --- l_[Mg/Fe] ? Limit flag for [Mg/Fe]
163-167 F5.2 --- [Mg/Fe] ? NLTE [Mg/Fe] abundance ratio
169-172 F4.2 --- e_[Mg/Fe] ? Uncertainty on [Mg/Fe]
174 A1 --- l_[Al/Fe] ? Limit flag for [Al/Fe]
176-180 F5.2 --- [Al/Fe] ? NLTE [Al/Fe] abundance ratio
182-185 F4.2 --- e_[Al/Fe] ? Uncertainty on [Al/Fe]
187 A1 --- l_[Si/Fe] ? Limit flag for [Si/Fe]
189-193 F5.2 --- [Si/Fe] ? NLTE [Si/Fe] abundance ratio
195-198 F4.2 --- e_[Si/Fe] ? Uncertainty on [Si/Fe]
200 A1 --- l_[S/Fe]LTE ? Limit flag for [S/Fe]
202-205 F4.2 --- [S/Fe]LTE ? LTE [S/Fe] abundance ratio (2)
207-209 F3.1 --- e_[S/Fe]LTE ? Uncertainty on [S/Fe]
211 A1 --- l_[K/Fe] ? Limit flag for [K/Fe]
213-217 F5.2 --- [K/Fe] ? NLTE [K/Fe] abundance ratio
219-222 F4.2 --- e_[K/Fe] ? Uncertainty on [K/Fe]
224 A1 --- l_[Ca/Fe] ? Limit flag for [Ca/Fe]
226-230 F5.2 --- [Ca/Fe] ? NLTE [Ca/Fe] abundance ratio
232-235 F4.2 --- e_[Ca/Fe] ? Uncertainty on [Ca/Fe]
237 A1 --- l_[Sc/Fe]LTE ? Limit flag for [Sc/Fe]
239-243 F5.2 --- [Sc/Fe]LTE ? LTE [Sc/Fe] abundance ratio (2)
245-248 F4.2 --- e_[Sc/Fe]LTE ? Uncertainty on [Sc/Fe]
250 A1 --- l_[Ti/Fe] ? Limit flag for [Ti/Fe]
252-256 F5.2 --- [Ti/Fe] ? NLTE [Ti/Fe] abundance ratio
258-261 F4.2 --- e_[Ti/Fe] ? Uncertainty on [Ti/Fe]
263 A1 --- l_[TiI/Fe] ? Limit flag for [TiI/Fe]
265-269 F5.2 --- [TiI/Fe] ? NLTE [TiI/Fe] abundance ratio
271-274 F4.2 --- e_[TiI/Fe] ? Uncertainty on [TiI/Fe]
276 A1 --- l_[TiII/Fe] ? Limit flag for [TiII/Fe]
278-282 F5.2 --- [TiII/Fe] ? NLTE [TiII/Fe] abundance ratio
284-287 F4.2 --- e_[TiII/Fe] ? Uncertainty on [TiII/Fe]
289 A1 --- l_[V/Fe]LTE ? Limit flag for [V/Fe]
291-295 F5.2 --- [V/Fe]LTE ? LTE [V/Fe] abundance ratio (2)
297-300 F4.2 --- e_[V/Fe]LTE ? Uncertainty on [V/Fe]
302 A1 --- l_[Cr/Fe] ? Limit flag for [Cr/Fe]
304-308 F5.2 --- [Cr/Fe] ? NLTE [Cr/Fe] abundance ratio
310-313 F4.2 --- e_[Cr/Fe] ? Uncertainty on [Cr/Fe]
315 A1 --- l_[Mn/Fe] ? Limit flag for [Mn/Fe]
317-321 F5.2 --- [Mn/Fe] ? NLTE [Mn/Fe] abundance ratio
323-326 F4.2 --- e_[Mn/Fe] ? Uncertainty on [Mn/Fe]
328 A1 --- l_[Fe/H] ? Limit flag for [Fe/H]
330-334 F5.2 --- [Fe/H] ? NLTE [Fe/H] abundance ratio
336-339 F4.2 --- e_[Fe/H] ? Uncertainty on [Fe/H]
341 A1 --- l_[FeI/H] ? Limit flag for [FeI/H]
343-347 F5.2 --- [FeI/H] ? NLTE [FeI/H] abundance ratio
349-352 F4.2 --- e_[FeI/H] ? Uncertainty on [FeI/H]
354 A1 --- l_[FeII/H] ? Limit flag for [FeII/H]
356-360 F5.2 --- [FeII/H] ? NLTE [FeII/H] abundance ratio
362-365 F4.2 --- e_[FeII/H] ? Uncertainty on [FeII/H]
367-371 F5.2 --- [Fe/H]LTE ? LTE [Fe/H] abundance ratio
373 A1 --- l_[Co/Fe] ? Limit flag for [Co/Fe]
375-379 F5.2 --- [Co/Fe] ? NLTE [Co/Fe] abundance ratio
381-384 F4.2 --- e_[Co/Fe] ? Uncertainty on [Co/Fe]
386 A1 --- l_[Ni/Fe]LTE ? Limit flag for [Ni/Fe]
388-392 F5.2 --- [Ni/Fe]LTE ? LTE [Ni/Fe] abundance ratio (2)
394-397 F4.2 --- e_[Ni/Fe]LTE ? Uncertainty on [Ni/Fe]
399 A1 --- l_[Cu/Fe] ? Limit flag for [Cu/Fe]
401-405 F5.2 --- [Cu/Fe] ? NLTE [Cu/Fe] abundance ratio
407-410 F4.2 --- e_[Cu/Fe] ? Uncertainty on [Cu/Fe]
412 A1 --- l_[Zn/Fe] ? Limit flag for [Zn/Fe]
414-418 F5.2 --- [Zn/Fe] ? NLTE [Zn/Fe] abundance ratio
420-423 F4.2 --- e_[Zn/Fe] ? Uncertainty on [Zn/Fe]
425 A1 --- l_[Sr/Fe] ? Limit flag for [Sr/Fe]
427-431 F5.2 --- [Sr/Fe] ? NLTE [Sr/Fe] abundance ratio
433-436 F4.2 --- e_[Sr/Fe] ? Uncertainty on [Sr/Fe]
438 A1 --- l_[Ba/Fe] ? Limit flag for [Ba/Fe]
440-444 F5.2 --- [Ba/Fe] ? NLTE [Ba/Fe] abundance ratio
446-449 F4.2 --- e_[Ba/Fe] ? Uncertainty on [Ba/Fe]
451 A1 --- l_[Eu/Fe] ? Limit flag for [Eu/Fe]
453-457 F5.2 --- [Eu/Fe] ? NLTE [Eu/Fe] abundance ratio
459-462 F4.2 --- e_[Eu/Fe] ? Uncertainty on [Eu/Fe]
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Note (1): C, CH and CI have been corrected also for evolutionary effects using
the Placco et al (2014) corrections (https://vplacco.pythonanywhere.com/).
Note (2): [N/Fe], [S/Fe], [Sc/Fe], [V/Fe] and [Ni/Fe] are provided only in LTE,
i.e. [N/Fe] = [N/H]_LTE - [Fe/H]_LTE. [Fe/H]_LTE is also provided.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star identifier
27- 69 A43 --- Ref Reference of the source paper
71- 74 A4 --- Ion Element/species identifier
76 A1 --- l_[X/H]LTE Limit flag for [X/H]
78- 83 F6.3 --- [X/H]LTE ? LTE [X/H] abundance ratio (1)
85- 89 F5.3 --- e_[X/H]LTE ? Uncertainty on [X/H]
91 I1 --- OCX [0/1]? Originally Corrected flag (2)
93 I1 --- OWX [0/1]? Other Wavelengths flag (3)
95-100 F6.3 --- d[X/H]NLTE ? NLTE abundance correction (4)
102 I1 --- ingrid[X/H] [0/1]? In Grid flag (5)
104-109 F6.4 --- s_d[X/H]NLTE ? Standard deviation of the NLTE correction
111-112 I2 --- o_d[X/H]NLTE ? Number of spectral lines used to
compute NLTE correction (6)
114-116 A3 --- LineType Line Type flag (7)
118-121 F4.2 --- PlaccoCor ? Placco evolutionary correction
for carbon (8)
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Note (1): In LTE unless originally published in NLTE, in which case OCX=1.
Note (2): Set to OCX=1 if [X/H] was published already corrected for
NLTE effects.
Note (3): Set to OWX=1 if [X/H] was derived from spectral lines not in our
line list (table1.dat).
Note (4): Averaged over the most commonly used spectral lines for species X that
are detectable at the specific stellar atmospheric parameters.
Note (5): Set to ingrid[X/H]=1 if stellar parameters fall within the NLTE grid
limits.
Note (6): Not given for CH and Cu, since the original studies do not provide
line-by-line corrections for these species.
Note (7): For Na, NaI and Al, AlI, as follows:
r = Abundance and NLTE correction based on resonance lines
s = Abundance and NLTE correction based on subordinate lines
all = NLTE correction based on both resonance and subordinate lines. Abundance
was either derived from both or the lines used were not specified in the
source paper.
Note (8): For C, CH, CI, computed using https://vplacco.pythonanywhere.com/
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 25 A25 --- Name Star identifier (1)
27- 69 A43 --- Ref Reference of the source paper
71- 72 I2 h RAh Right Ascension (J2000)
74- 75 I2 min RAm Right Ascension (J2000)
77- 81 F5.2 s RAs Right Ascension (J2000)
83 A1 --- DE- Declination sign (J2000)
84- 85 I2 deg DEd Declination (J2000)
87- 88 I2 arcmin DEm Declination (J2000)
90- 94 F5.2 arcsec DEs Declination (J2000)
96-101 F6.1 K Teff ? Effective temperature
103-107 F5.2 [cm/s2] logg ? Surface gravity
109 A1 --- l_[Fe/H] Limit flag for [Fe/H]
111-115 F5.2 --- [Fe/H] ? [Fe/H] abundance ratio (2)
117-121 F5.3 --- e_[Fe/H] ? Uncertainty on [Fe/H]
123-147 A25 --- SAGAname Name of star in SAGA (3)
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Note (1): A unique name per star, following alphabetic order.
Note (2): Given in LTE unless it was originally published in NLTE
(OCFe=1 in table4.dat).
Note (3): Multiple names may refer to the same object.
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Acknowledgements:
Ioanna Koutsouridou, ioanna.koutsouridou(at)unifi.it
(End) Patricia Vannier [CDS] 13-May-2025